Soft photon production in the boost-invariant color-flux tube model

Starting from the classical expressions for emission of radiation we calculate soft photon production in the boost-invariant color-flux tube model. In the center-of-mass system of the initial tube we find that for large energies (√s∼20 GeV) the production of photons with frequencies: 20 MeV<ω<50 MeV, and emitted perpendicularly to the collision axis is strongly enhanced; it exceeds considerably production of photons given by the Low limit. For the emission more collinear with the collision axis and for decreasing ω the effect becomes weaker and, eventually, in the limit ω=0 we recover precisely the Low formula. We also find that for smaller energies (√s∼5 GeV) the emission of photons is well reproduced by the Low formula. Generally speaking, the observed enhancement is related to the existence of a large, i.e. extended in time, region of photon emission. This, in turn, results from the time dilation accompanying the spacetime evolution of tubes. Strong time dilation effects follow from the boost-invariance of our model and, for larger s, considerably enhance radiation of soft photons. By the same token, this enhancement decreases with decreasing s, because dilation decreases. (orig.)